1. Technical Field
The disclosure relates to a solar cell with a trench structure for isolation function and manufacturing method thereof, and particularly to a hetero junction silicon crystalline solar cell and manufacturing method thereof.
2. Related Art
Due to the increasing demand for eco-friendly electricity sources, electricity is no longer merely supplied from main electricity suppliers (such as thermal power generation, nuclear power generation, etc.). Alternative kinds of clean energy have been increasingly focused on. In comparison with other types of energy, solar energy has a higher electricity generation efficiency and broader applicability; consequently, the development of various kinds of solar cells has been increasingly and continuously making breakthroughs.
Among the various kinds of solar cells, the tandem structure solar cell optimizes its photoelectric conversion efficiency by combining materials with different energy gaps, thus performing higher photoelectric conversion efficiency. As compared to a conventional silicon based solar cell, the hetero junction silicon crystalline solar cell includes an intrinsic amorphous silicon semiconductor/P-type semiconductor layer (i/p layer), and an intrinsic amorphous silicon semiconductor/N-type semiconductor layer (i/n layer), which are very thin and respectively grown on the two surfaces of the crystalline silicon semiconductor substrate of the hetero junction silicon crystalline solar cell. The hetero junction silicon crystalline solar cell possesses advantages of simple structure, high open circuit voltage, applicable to thin substrate, low manufacturing temperature, etc.
The manufacturing process of the conventional hetero junction silicon crystalline solar cell is described briefly here. Firstly, intrinsic amorphous silicon semiconductor layer with thickness thereof smaller than 10 nanometers is grown on the crystalline silicon semiconductor substrate using plasma enhanced chemical vapor deposition (PECVD), and is provided for passivation. Then, an amorphous silicon semiconductor layer of a thickness less than 20 nanometers is formed on the intrinsic amorphous silicon semiconductor layer; the conductive type of the amorphous silicon semiconductor layer is different from that of the crystalline silicon semiconductor substrate, thus forming p-n junctions. Finally, vacuum evaporation is applied to manufacture the transparent layer and the front and back electrodes, thereby accomplishing the manufacturing of the hetero junction silicon crystalline solar cell.
However, during the vacuum evaporation the coating formed on the front surface of the solar cell contacts with the coating formed on the back surface of the solar cell, leading to short circuits; as a result, an insulating process is applied to keep the front electrode from being connected electrically to the back electrode. Conventionally, after the vacuum evaporation process, a laser beam is applied to form a trench on the solar cell to solve the short circuit issue; nevertheless, upon application of the laser beam, the instant high energy provided by the laser beam may induce the amorphous silicon semiconductor layer to become microcrystallized, thereby resulting in a further severe short circuit issue and reducing photoelectric conversion efficiency.